1. Field of the Invention
This invention relates generally to the field of marine fuel systems and more particularly to marine fuel systems comprising a backflow prevention and overfill alarm system.
2. Description of Related Art
Fueling of marine vessels is a frequent and necessary task for all vessel operators. Marine vessels typically have an internally mounted fuel tank for storing liquid fuel, and supplying fuel to one or more internal combustion engines for propulsion. The fuel tank is typically mounted within the vessel and includes a fuel fill inlet or filler line that extends from the tank to an fill port or access point on the vessel, such as on the deck, and a vent line that extends from the tank to allow for ventilation of the tank to prevent the undesired build-up of vapor pressure.
As noted above, fuel systems used on marine vessels typically include a vent line from the fuel tank. The vent line opens to the atmosphere above the water-line. The vent line permits air to escape from the tank as the tank is being refueled. The vent line also enables air to enter the tank as fuel is withdrawn for delivery to the engine. A significant problem with conventional fuel tank vent lines is the potential for fuel spillage. For example, air flowing out of the vent line can carry fuel overboard and into the water. In addition, wave action can rock the vessel sufficiently to cause fuel to be discharged overboard through the vent line. In addition, thermal expansion can also cause fuel, particularly from a full tank, to be discharged overboard through the vent line. Another significant problem can be encountered during the fueling of marine vessels. More particularly, the spillage of fuel into the environment due to overfilling, whereby fuel escapes through the vent line or fuel fill port, is a persistent environmental issue that has heretofore not been successfully addressed. The problem generally occurs due to the fuel filling attendant's failure to shut-off or terminate fuel flow when the vessel's fuel tank is filled thereby causing fuel to backflow through the fuel fill inlet line and ultimately spill from the vent port and/or fill port.
As a result of these problems, the background art reveals a number of attempts directed to addressing fuel spillage from marine vessels. Those attempts include disclosures directed to capturing spilled fuel by use of spillage containers removably attached to the side of the boat as disclosed in U.S. Pat. Nos. 4,802,125 (Wilson et al.) and 4,802,514 (Morse).
Further advancements include, U.S. Pat. No. 3,187,935, issued to Lense, which discloses a venting device for fuel tanks having a pair of vent pipes that terminate in the tank at opposite ends thereof. Since both ends of the fuel tanks are “vented” the tank is always properly vented regardless of the orientation of the vessel.
U.S. Pat. No. 4,724,861, issued to Covert et al., discloses a fuel tank venting system having a relatively complex mechanical apparatus that functions to inhibit the flow of fuel vapor.
U.S. Pat. No. 5,322,099, issued to Langlois, discloses an apparatus for preventing the spillage of fuel into the water when filling a fuel tank of a marine vessel. A valve assembly installed in the vent line, and an overflow container is disposed in the vent line between the valve assembly and the vent port. The valve assembly includes a drain hole for permitting small quantities of fuel to pass through the valve assembly and into the overflow container. A fill container is used to capture fuel when filling the fuel tank. U.S. Pat. No. 5,515,891, issued to Langlois, discloses an apparatus for preventing fuel spillage that also includes the installation of an overflow container and valve assembly in the vent line. A fill container is used when filling. The fill container includes a float that provides a visual indication when the tank is full. A by-pass line is coupled between the fill container and the overflow container. U.S. Pat. No. 5,950,688, issued to Langlois, discloses another apparatus for preventing fuel spillage when filling a fuel tank on a vessel. In this patent Langlois discloses installation of a fill container (212) to the fuel fill line. A drain or vent line (307) operates to vent gases present in the system as well as preventing the formation of a vacuum.
U.S. Pat. No. 7,380,542, issued to Herrington, discloses a fuel vent tank for marine craft. A collection tank is mounted in the vent line from the main fuel tank. Fuel escaping the main tank through the vent line enters the collection tank. A float switch is connected to a warning light.
The disclosures of the background art generally disclose overly complex systems that are inherently ineffective and/or unreliable. In addition, many of the systems disclosed in the background art rely on check valves to stop the flow of fuel through the vent line. The use of check valves is considered particularly undesirable since mechanical valves are prone to failure, and should the valve become stuck in a closed configuration pressure could quickly rise in the fuel system leading to a potentially catastrophic explosion resulting in loss of life and/or loss of the vessel. Such systems fail to comply with standards set forth by the American Boat and Yacht Council (ABYC) that require fuel tank vent systems not to restrict the continuous release of vapor. Accordingly, there remains a need in the art for advancements in the field of marine fuel filling systems to prevent the environmental contamination due to the unintended spillage of fuel during the fueling process.